Cell-mediated immunity is impaired in patients with Hodgkin's disease both chemically and in vitro. Certain defects in cell-mediated immunity have been shown to persist after successful therapy of the disease. Thus, the aberrations in cell-mediated immunity may play a significant role in the pathogenesis of Hodgkin's disease. The exact mechanism(s) contributing to the impaired cell-mediated immunity in Hodgkin's disease patients are not well established. Altered T-cell function and altered peripheral blood monocyte function both have been demonstrated to occur in patients with Hodgkin's disease. Recently, the malignant cell in Hodgkin's disease, the Reed-Sternberg cell, has been shown to be of monocyte-macrophage origin. For these reasons prospective evaluation of cell-mediated immune functions with emphasis on the role of the peripheral blood monocyte in Hodgkin's disease patients may clarify the exact nature of the immune defects in these patients. The objectives of this research are to study a variety of cell-mediated immune functions including allogeneic and autologous mixed lymphocyte reactions, phytohemagglutinin response, T-cell helper function in pokeweed mitogen-stimulated cultures, peripheral blood monocyte growth characteristics in cell culture with examination of monocyte mediators released into the conditioned media and the malignant potential of the peripheral blood monocyte in Hodgkin's disease patients. The question of whether inherent T-cell abnormalities, or monocyte abnormalities or abnormal cell-cell interactions are responsible for the impaired cell-mediated immunity will be examined. Production by Hodgkin's T\cells also is being evaluated.